1. Field of the Invention
The present invention relates to a vacuum type switch gear device having an L shaped stationary and movable conductors arrangement and, more specifically, to a composite vacuum type switch gear device in which an arrangement between a movable conductor and arc grooves provided for a movable electrode carried by the movable conductor is, in particular, improved.
2. Conventional Art
In a vacuum circuit breaker, making and breaking operation is performed by opening and closing a pair of electrodes disposed in an opposing manner within a vacuum bulb. Generally, through vertical displacement of a movable rod or conductor with respect to a stationary rod or conductor by means of an operating mechanism disposed outside the vacuum bulb, electrodes provided each at an end of the respective rods are opened and closed.
Further, in the vacuum circuit breaker disclosed in JP-A-55-143727 (1980), a movable electrode is designed to be rotatable around a main axis so as to open and close the same with respect to a stationary electrode.
Generally, when an arc stays at a portion between both electrodes during circuit breaking operation of a circuit breaker, the surface temperature of each of the electrodes increases due to thermal energy input from the arcing to thereby cause melting of the metal of the electrodes. In such instance, consumption of the electrodes is significant and, as well surplus vapour metal particles produced between the electrodes extremely reduce circuit breaking performance.
Therefore, in vacuum circuit breakers, and in particular, those for interrupting a large current, a variety of measures have been proposed for the structure of the arc electrodes. For example, with arc electrodes having a plurality of spiral arc grooves, an arc generated between the electrodes is applied of a driving force in a circumferential direction by a current flowing through both electrodes and is always moved between both electrodes to thereby suppress the melting of the metal surface of the electrodes and to improve its circuit breaking performance.
However, with the conventional movable conductor or rod rotatable type vacuum circuit breaker as mentioned above which makes use of electrodes having spiral arc grooves, an arc generated between the electrodes is subjected to an additional electric-magnetic force due to magnetic fluxes induced by a current flowing through the movable conductor located near the electrodes. As a result, an area on the electrode on which an arc can be ignited, namely an effective arcing area on the electrode, is limited to thereby reduce the circuit breaking performance thereof.